Should Tuna Smell Fishy? A Guide to Tuna Freshness

Tuna is one of the most popular fish worldwide thanks to its versatility, affordability, and nutritional value. But there’s an ongoing debate around how tuna should smell. Some say any “fishy” odor in tuna means it’s gone bad. Others argue a slight fishy smell in tuna is totally normal. So what’s the real verdict – should tuna smell fishy or not?

In this comprehensive guide, we’ll cover:

• The science behind fish smells
• Factors that affect tuna’s smell
• How to tell if tuna smells right or wrong
• Tips to prevent and reduce fishy odors in tuna
• When to toss tuna out due to smell

Let’s dig in!

The Science Behind Fishy Smells

To understand tuna smells, we first need to know why fish smell “fishy” at all.

Fish flesh doesn’t naturally have a strong odor The fishy smell comes from compounds like

• Trimethylamine oxide – converted to trimethylamine (TMA) by bacteria after death
• Cadaverine and putrescine – breakdown products of amino acids
• Fatty acids like EPA and DHA

These compounds are normal in live fish at low levels. But after death, bacteria grow rapidly, increasing TMA and other byproducts that make the fishy stench.

So some fishy odor right after catching is normal. But it intensifies as the fish ages and more bacteria multiply.

Now let’s see how this applies specifically to tuna.

Factors That Affect Tuna’s Smell

Several key factors impact the smell of tuna:

Oil content

• Fattier tuna like bluefin develop stronger smells from lipid oxidation and fatty acid breakdown.

• Leaner tuna like skipjack have milder odor.

Storage temperature

• Heat speeds up bacteria growth and chemical reactions that produce smelly compounds.

• Keeping tuna chilled suppresses these reactions.

Freshness

• Tuna smells more strongly as it ages post-catch due to accumulating waste metabolites.

• Ultra-fresh tuna has barely any smell.

Processing method

• Live tuna is nearly odorless. Smell increases after death.

• Canning cooks the tuna, reducing some smells. But it still retains some fish oil odors.

So tuna smell varies based on factors like fat content, storage, age, and processing. This means some fishy odor is to be expected! Now let’s see how to tell if it’s normal or problematic.

How to Tell if Tuna Smells Right or Wrong

Since some fishy smell in tuna is natural, at what point does the smell indicate spoilage? Here are some guidelines:

Fresh tuna

• Should have very mild, neutral smell. Some ocean water scent is fine.

• Little to no ammonia, sweet, or byproduct odors.

• Leaner tuna like skipjack may have almost no scent.

• Fattier tuna like bluefin may have slight fatty/meaty smells.

Aged tuna

• Increasingly stronger briny, fishy scent, especially in oily tuna.

• Noticeable ammonia, sweet, sour, or rotten smells indicate spoilage.

Canned tuna

• Has more cooked aroma with some residual fishiness.

• Shouldn’t have strong or sharp chemical odors.

• Unpleasant bitter, vinegar, sulfur smells are warning signs.

Rotten tuna

• Intense foul, fishy, ammonia, acidic smell.

• Potent garlic, cheese, bile or decaying odor.

• You’ll have no doubt it’s spoiled based on extreme stench.

So if the tuna stench seems overpowering, that’s a red flag. But a light fishy smell alone doesn’t mean the tuna is bad.

Tips to Prevent and Reduce Fishy Tuna Smells

If you find tuna’s odor too strong, there are some tricks to help reduce it:

• Buy the freshest tuna possible, preferably sashimi-grade.

• Keep tuna chilled at all times to inhibit bacteria growth.

• Rinse canned tuna to remove some excess oils causing smell.

• Add lemon, vinegar, onions, or other acids to help neutralize amines.

• Marinate tuna in wine, soy sauce, or other marinades to mask smells.

• Cook tuna well using spices – this diminishes volatile compounds.

• Opt for milder-smelling tuna like skipjack if scent bothers you.

Proper handling and cooking practices go a long way in limiting fishy odors.

When to Toss Tuna Out Due to Smell

At what point should you say no way to stinky tuna? Here are some signs tuna has gone bad and needs discarding:

• Putrid, gag-inducing rotten stench

• Strong bitter, medicinal, ammonia smell

• Slimy, mushy flesh with foul odor

• Mold or white spots visible on tuna

• Rancid or “off” smell unlike normal fishy scent

• Discoloration or unnatural colors in flesh

• Tuna well past freshness date or recently left unrefrigerated

Don’t risk getting sick from eating rotten or rancid tuna! The smell provides crucial cues to its safety.

The Verdict on Tuna Smell

So back to our original question – should tuna smell fishy? The answer is…sometimes!

It’s normal and expected for fresh tuna to have mild fishy, meaty scents, especially for fatty varieties like bluefin. This smell intensifies as tuna ages but doesn’t necessarily mean spoilage.

However, strong foul odors do indicate tuna has gone bad and should be discarded.

To recap:

• Light fishy smell in tuna is normal based on science.

• Odor varies based on fat content, age, storage, and processing.

-judge tuna freshness by smell’s strength and type, not just presence.

• Use tips like rinsing, marinating, and cooking to reduce unpleasant smells.

• Throw out tuna with potent foul, rotten stench to be safe.

So aim for the freshest tuna possible, store it properly, and use your nose as a guide. With an understanding of the science behind tuna smells, you can feel confident determining if your tuna passes the sniff test or ends up in the trash!